Serperior, The Regal Pokémon. It can stop its opponents with its glare. It only fights formiddable opponents and intimidates them with its head held high. It can store sunlight energy in its body

Overview

The most popular starter this gen, Serperior is a pretty standard Grass type. Good Speed, like Sceptile, good defences, like Meganium, and lacklustre offences... like Meganium. However, the Grass snake has access to one of the best abilities in the game... Contrary. Basically, stat changes are reversed. Yes, it works with Leaf Storm. Yes, it's ridiculously good. No, it doesn't exist yet. That's right, Serperior has not been released into the Dream World yet, so I hope you like your subpar Overgrow Serperior. I'll still be including Contrary, but I needed to say it doesn't exist at the time of this POTW.

Abilities

Overgrow: boosts Grass moves in a pinch. It's alright, but eh... nothing compared to its Dream World ability.Contrary: this ability makes Serperior the best Grass starter of all time. Yeah, Venusaur is good, but it doesn't have Contrary. Yep, Sceptile is pretty good too! Doesn't have Contrary though, does it? Meganium is pretty... uh... Serperior is the best.

Nice Speed, nice bulk, and a good support movepool, Serperior makes for a good screens lead. Reflect and Light Screen make all of your Pokémon tanks, as it gives the team a +2 to their defences whilst the screens are up. Taunt stops you from being taunted, and also stops entry hazards like Stealth Rock from being set up. Leech Seed encourages switches and gives you a little recovery and a little more damage. Glare got a nice boost this gen, and it now has 90% accuracy. Glare is especially cool because unlike Thunder Wave, it can paralyze Ground types. Leaf Storm is amazing, especially with Contrary. However, it's still a good move even without it. If you don't want the Special Attack reduction, run Grass Knot, Energy Ball, or Giga Drain.

I don't think there's a Grass type that doesn't use SubSeed. Substitute to protect from damage, and use Leech Seed whilst you are temporarily invulnerable. The recovery from Leech Seed also fuels more uses of Substitute. Dragon Tail is usable over Leech Seed. Leaf Storm is crazy power, but should only be used with Contrary on this set. Energy Ball is more reliable. Grass Knot potentially has 120 base power depending on the opponent's weight. Giga Drain absorbs more health for you to use on Substitute. Hidden Power [Ice] wrecks Dragon/Flying Pokémon. Hidden Power [Fire] beats Ferrothorn and Forretress.

Glare is a great support move as it paralyzes... everything! Taunt stops entry hazards, healing, anything like that. Always a great move, especially when combined with Leech Seed. Dragon Tail phases the opponent and deals a little damage. Like Roar and Whirlwind, Dragon Tail has negative priority. The Grass move is whatever you want. Leaf Storm if you are running Contrary, and whatever you want if you aren't.

Choice Specs Leaf Storm hurts. +2 Special Attack Choice Specs Leaf Storm hurts more. Hidden Power [Fire] sorts out Ferrothorn and Forretress, whereas Hidden Power [Ice] stops any Dragons from trying to wall you. Glare... is there because Serperior's movepool is pathetic. Giga Drain or Grass Knot exist for when Leaf Storm runs out of PP, or if you are using Overgrow and needed a reliable attack, but Dragon Tail can hit counters on the switch, allowing you to scout and see what they want to bring in.

EVs & Natures

Double Screens
240 Speed gets you above the genies, which are base 111. Max Special Attack makes Leaf Storm hit as hard as possible, although you could run 252 HP/16 SAtk/240 Speed instead.

Every Grass Pokémon's set
Max Speed is always an option, but it seems like a waste to me. You don't want max HP on this set, as you will get a larger percentage of HP back with each drain from Leech Seed if you max HP is lower..

Support snake
Max HP for general bulk. Enough Speed to outrun neutral base 90s. I like the rest in Defence personally, but you can put it in Special Defence or Special Attack.

Choice
Max Special Attack and max Speed is a good plan. You can drop the Speed lower, but eh... max Speed is more important on a choice set.

Other Options

Calm Mind, Growth, Leaf Blade Mean Look, Mirror Coat, Coil, Swords DanceCalm Mind is a cool move, but it is wasted on Serperior. It has a better way of boosting its Special Attack.Growth can be used on some mixed sweeper set but the Grass snake's movepool is so awful, it isn't worth it.
On sets where the only move is a special Grass move, Leaf Blade is an option if you wanted to go physical. The high crit chance may come in handy, so running physical is a pretty good choice.Mean Look prevents the opponent from switching. It's alright... I guess you can combine it with Leech Seed and stall them out.Mirror Coat reflects Special damage at the foe. Special version of Counter, basically.Coil boosts your Attack, Defence and Accuracy... not worth it on a sweeping set, but I think with Dragon Tail it could be usable.Swords Dance doubles your Attack, but as Serperior has Leaf Blade, Return, Iron Tail and Rock Smash as physical attacks, it is pointless.

Double & Triple Battle Options

Serperior's main tactic is to boost its Special Attack through Leaf Storm. This does not translate too well to multi Pokémon battles. Serperior has such... a terrible movepool that it is so predictable in such a fast hard hitting metagame. It can't stall for Leech Seed, it won't be allowed to spam Leaf Storm to get strong, it'll just be dead in the water. I honestly can't see why you'd run Serperior in doubles or triples, as I cannot see any benefits. If anyone knows any, feel free to contact me and school me.

Partners

Anything that can block Fire, Ice, Bug and Poison works. Hey! Heatran! Yep, like with all other Grass Pokémon, Heatran is a fantastic partner. Chandelure also works well, just be careful if you are switching it into stuff, as it is pretty frail. Keep Toxic Spikes and Toxic away from Serperior. Either run a cleric, a spinner, or a Poison Pokémon to absorb the Toxic Spikes. Honestly, there isn't much to say. Serperior is a standard Grass type. Stick to being able to switch into its counters, so you will always be one step ahead.

Countering Serperior

Countering something with base 113 Speed, a massively damaging attack that works as a free Nasty Plot, a draining attack that keeps it healed and that is often behind a Substitute. Well, straight away we look to the Steel Pokémon. Forretress, Scizor, Skarmory, Ferrothorn, Registeel, Bronzong, Metagross, Jirachi, the list is huge. But yeah, they are your best switch ins to Leaf Storm. Just avoid Hidden Power [Fire]. Speaking of Fire, how about Heatran? Resists Leaf Storm, destroys in one hit, awesome. Don't get Glared though... that'd suck. Resisting Leaf Storm is the key here... Salamence, Chandelure, bulky Grass types, if you don't resist Leaf Storm, you will be going down. Blissey and Chansey work as switch ins, but they are such insane Leech Seed bait that you will be healing Serperior more than you are damaging it. Taunt messes Serperior up pretty badly. Pressure whittles down Leaf Storm's low PP quite quickly, ideally allowing you to jump in and phaze all of its boosts. Honestly... Serperior is only worth using if you are using Contrary. Sure, it has nice Speed and dual screens... that's literally it. Contrary is the only redeeming thing about Serperior. Otherwise, it is sitting very close to the bottom of the Grass starter pile.